Laminate for use in armor of cell, and secondary cell

ABSTRACT

The present invention relates to a laminate for battery encasement comprising aluminum foil and an inner layer, wherein a resin film layer that comprises an aminated phenol polymer (A), a trivalent chromium compound (B), and a phosphorus compound (C) lies between the aluminum foil and the inner layer. The laminate for battery encasement of the present invention is excellent in adhesiveness, gas impermeability, etc., and therefore can be suitably used as a material for encasing a secondary battery, particularly a lithium ion polymer secondary battery.

TECHNICAL FIELD

[0001] The present invention relates to a laminate for use in a batteryencasement of a secondary battery, such as a lithium ion battery and thelike, particularly a lithium ion polymer secondary battery using a gelelectrolyte.

BACKGROUND ART

[0002] Lithium ion secondary batteries are widely used in various kindsof electronic devices and components, particularly in portabletelephones, note-book personal computers, video cameras, satellites,electric motorcars, etc.

[0003] Among lithium ion secondary batteries, the lithium ion polymersecondary battery uses a gel electrolyte containing a conductive polymeror the like as its electrolyte. Compared to a lithium ion battery thatuses a nonaqueous electrolyte, a lithium ion polymer secondary batteryis very safe because the possibility of leakage of the electrolysissolution is low, and the lithium ion polymer secondary battery can bemade smaller and lighter in weight. Therefore, the lithium ion polymersecondary battery is one of the batteries that is expected to increaseits market demand.

[0004] From the viewpoint of productivity, quality stability and thelike, as an encasement for lithium ion polymer secondary batteries, ametallic can of cylindrical shape, a rectangular parallelepiped shape orthe like, that is obtained by press molding a metal plate, metal foiland the like is generally used.

[0005] However, when a metal can is used as an encasement for asecondary battery, the shape and design of the battery itself aresubject to many restrictions and the electronic device or component thatis equipped with the battery with a metal can encasement is also subjectto restrictions on the shape and design of the part in which the batteryis stored. This leads to the problem that the electronic devices andcomponents cannot be formed into a desirable configuration, making itdifficult to render the electronic devices and components furtherminiaturized and lighter in weight.

[0006] Therefore, in order to form an electronic device and componentinto a desired configuration and achieve further miniaturization andlightening in weight thereof, development of a battery encasement thatcan be readily formed into a shape that fits the shape of the electronicdevice or electronic component has been desired. As a metal to be usedfor battery encasement, aluminum foil is attracting widespreadattention.

[0007] A laminate for battery encasement for use in a lithium ionpolymer secondary battery should have the properties that meet thefollowing requirements.

[0008] (1) The laminate should have a gas barrier properties that caninsulate the principal part and the electrodes in the main body of thesecondary battery from outside air (particularly containing water vapor)in order to avoid the undesirable phenomenon of hydrofluoric acidgenerated by hydrolysis of the electrolyte corroding the aluminum foil,when water vapor enters into the encasement for a secondary battery fromoutside.

[0009] (2) The innermost layer of the laminate should exhibit excellentadhesiveness to the metal electrodes that compose the secondary batteryand excellent adhesiveness between the innermost layers.

[0010] (3) The secondary battery should have properties (heat resistanceand cold resistance) resistive to the temperatures at which the batteryis used, specifically, the temperature in an automobile during thesummertime, in a cold district during the wintertime, etc. Thetemperature in the secondary battery is further increased by charging ordischarging during use of the secondary battery. Even when the secondarybattery is used under these severe circumstances, as a batteryencasement, the laminate should have stable thermal adhesiveness, gasbarrier properties, etc.

[0011] (4) The adhesive strength between layers should not be weakenedby the gel electrolyte (gel electrolysis solution) that is used in thesecondary battery.

[0012] (5) The laminate for battery encasement should be resistant tocorrosion by hydrofluoric acid generated by deterioration, hydrolysis,or the like of the gel electrolyte used in the secondary battery.

[0013] (6) The laminate for battery encasement should have thedrawability and the like to be easily shaped into a desirable shape, andbe excellent in productivity.

[0014] However, a laminate for battery encasement having such excellentproperties has not yet been developed.

DISCLOSURE OF THE INVENTION

[0015] One object of the present invention is to provide a laminate forthe encasement of a lithium ion polymer secondary battery that hasexcellent gas impermeability.

[0016] Another object of the present invention is to provide a laminatefor the encasement of a lithium ion polymer secondary battery whereinthe adhesive strength between the layers is not substantially decreasedby the gel electrolyte (gel electrolysis solution) that is used in thesecondary battery.

[0017] Still another object of the present invention is to provide alaminate for use in an armor of a lithium ion polymer secondary batterythat exhibits, as a material for battery encasement, stable thermaladhesiveness, gas barrier properties, etc., even when the secondarybattery is used under severe conditions.

[0018] The present inventors conducted extensive research and foundthat, regarding a laminate for battery encasement that is formed bylaminating aluminum foil and an inner layer, it is possible to obtain adesirable laminate for battery encasement by laying a specific resinfilm layer between the aluminum foil and the inner layer. The presentinvention is accomplished based on this finding.

[0019] The present invention provides a laminate for battery encasementthat comprises aluminum foil and an inner layer, wherein a resin filmlayer comprising an aminated phenol polymer (A), a trivalent chromiumcompound (B), and a phosphorus compound (C) is interposed between thealuminum foil and the inner layer.

[0020] The present invention provides a laminate for battery encasement,wherein the contents of the aminated phenol polymer (A), the trivalentchromium compound (B), and the phosphorus compound (C), per 1 m² of theabove resin film layer, are about 1 to 200 mg, about 0.5 to 50 mgcalculated as chromium, and about 0.5 to 50 mg calculated as phosphorus,respectively.

[0021] The present invention provides a laminate for battery encasement,wherein the inner layer is composed of an olefin-based thermal adhesiveresin and has a thickness of 10 to 100 μm.

[0022] The present invention provides a laminate for battery encasement,wherein the inner layer comprises two or more layers, of which theinnermost layer is composed of an olefin-based thermal adhesive resinand has a thickness of about 10 to 100 μm.

[0023] The present invention provides a laminate for battery encasement,wherein the aluminum foil is a soft aluminum foil having a thickness ofabout 15 to 100 μm.

[0024] The present invention provides a laminate for battery encasement,wherein an outer layer is provided on the aluminum foil on the sideopposite to the surface where the resin film layer is formed.

[0025] The present invention provides a laminate for battery encasement,wherein the contents of the aminated phenol polymer (A), the trivalentchromium compound (B), and the phosphorus compound (C), per 1 m² ofresin film layer that lies between the outer layer and the aluminumfoil, are about 1 to 200 mg, about 0.5 to 50 mg calculated as chromium,and about 0.5 to 50 mg as calculated as phosphorus, respectively.

[0026] The present invention provides a secondary battery that comprisesthe above-described laminate for battery encasement as the encasementthereof.

[0027] The present invention provides a lithium ion polymer secondarybattery that comprises the above-described laminate for batteryencasement as the encasement thereof.

[0028] The laminate for battery encasement according to the presentinvention comprises an aluminum foil and an inner layer, wherein a resinfilm layer that comprises an aminated phenol polymer (A), a trivalentchromium compound (B), and a phosphorus compound (C) lies between theinner layer and the aluminum foil.

[0029] Aluminum Foil

[0030] Aluminum foil serves as a gas barrier layer that prevents gases,such as water vapor, oxygen gas, etc., from penetrating into thebattery.

[0031] From the viewpoint of reliable gas barrier properties,processability during the processing step, etc., it is preferable thatthe thickness of the aluminum foil be generally about 15 to 100 μm andpreferably about 20 to 80 μm.

[0032] It is preferable that the aluminum foil be a soft aluminum foil.

[0033] Resin Film Layer

[0034] The resin film layer is provided in order to firmly adhere thealuminum foil to the inner layer and to protect the inner layer side ofthe aluminum foil from the gel electrolyte and hydrofluoric acid that isgenerated by deterioration or hydrolysis of the gel electrolyte.

[0035] The resin film comprises an aminated phenol polymer (A), atrivalent chromium compound (B), and a phosphorus compound (C). Thesethree ingredients bond to each other through coordinate bonds, covalentbonds and like chemical bonds, or they strongly bond to the aluminumfoil or adhere to the aluminum foil through these chemical bonds.

[0036] Particularly, when the inner layer that is adjacent to the resinfilm is an olefin-based heat adhesive resin layer, hydroxyl group andlike polar groups in the aminated phenol polymer (A) further enhance theadhesive strength between the resin film layer and the inner layer(interlaminar strength).

[0037] The resin film layer of the present invention is hardly solublein water, aqueous acids such as hydrofluoric acid and the like, organicsolvents, etc., and exhibits excellent corrosion-resistance.

[0038] In the present invention, the above three ingredients (A) to (C)synergistically interact with each other and exhibit excellentcorrosion-resistance to the gel electrolyte and deteriorated gelelectrolyte, maintaining high adhesiveness of the resin film layer tothe inner layer, and particularly, to an olefin-based heat adhesiveresin layer.

[0039] The content of the aminated phenol polymer (A) contained in theresin film layer is suitably selected taking corrosion-resistance,press-moldability, and the like into consideration.

[0040] The content of the trivalent chromium compound (B) contained inthe resin film layer is suitably selected taking thecorrosion-resistance, economical efficiency, and the like intoconsideration.

[0041] The content of the phosphorus compound (C) contained in the resinfilm layer is suitably selected taking adhesiveness and the like intoconsideration.

[0042] In the present invention, per 1 m² of resin film layer, it ispreferable that the content of the aminated phenol polymer (A) be about1 to 200 mg, the content of the trivalent chromium compound (B) be about0.5 to 50 mg calculated as chromium, and the content of the phosphoruscompound (C) be about 0.5 to 50 mg calculated as phosphorus, and morepreferably the content of the aminated phenol polymer (A) be about 5 to150 mg, the content of the trivalent chromium compound (B) be about 1 to40 mg calculated as chromium, and the content of the phosphorus compound(C) be about 1 to 40 mg calculated as phosphorus.

[0043] In other words, in the present invention, per 1 m² of resin filmlayer, it is preferable that the content of the aminated phenol polymer(A) be about 1 to 200 parts by weight, the content of the trivalentchromium compound (B) be about 0.5 to 50 parts by weight calculated aschromium, and the content of the phosphorus compound (C) be about 0.5 to50 parts by weight calculated as: phosphorus, and it is more preferablethat the content of the aminated phenol polymer (A) be about 5 to 150parts by weight, the content of the trivalent chromium compound (B) beabout 1 to 40 parts by weight calculated as chromium, and the content ofthe phosphorus compound (C) be about 1 to 40 parts by weight calculatedas phosphorus.

[0044] The above-described resin film layer is extremely thin and thefilm thickness thereof is generally at the nano-order level.

[0045] Aminated Phenol Polymer (A)

[0046] For the aminated phenol polymer (A), various known kinds can beused, including the aminated phenol polymers mentioned below.

[0047] (1) Aminated phenol polymers having a repeating unit representedby general formula (I),

[0048] wherein X represents a hydrogen atom, hydroxyl group, alkylgroup, hydroxyalkyl group, allyl group, or benzyl group; and

[0049] a repeating unit represented by general formula (II),

[0050] wherein X is the same as defined above and R¹ and R² are the sameor different to each other and represent hydroxyl group, alkyl group, orhydroxyalkyl group.

[0051] (2): Aminated phenol polymers consisting of the repeating unitrepresented by the above general formula (II).

[0052] (3): Aminated phenol polymers having a repeating unit representedby general formula (III),

[0053] wherein X is the same as defined above; and

[0054] a repeating unit represented by general formula (IV),

[0055] wherein X, R¹, and R² are the same as defined above.

[0056] (4): Aminated phenol polymers consisting of a repeating unitrepresented by general formula (IV).

[0057] In the above general formulae (I) to (IV), examples of alkylgroups represented by X, R¹, and R² include methyl group, ethyl group,n-propyl group, iso-propyl group, n-butyl group, iso-butyl group,tert-butyl group and like C₁ to C₄ straight or branched chain alkylgroups. Examples of hydroxyalkyl groups represented by X, R¹, and R²include hydroxymethyl group, 1-hydroxyethyl group, 2-hydroxyethyl group,1-hydroxypropyl group, 2-hydroxypropyl group, 3-hydroxypropyl group,1-hydroxybutyl group, 2-hydroxybutyl group, 3-hydroxybutyl group,4-hydroxybutyl group and like C₁ to C₄ straight or branched chain alkylgroups wherein one of the hydrogen atoms is substituted by hydroxyl.

[0058] It is preferable that X represented by general formulas (I) to(IV) be a hydrogen atom, a hydroxyl group, or a hydroxyalkyl group.

[0059] It is preferable that the aminated phenol polymers mentioned initem (1) be aminated phenol polymers that contain the repeating unitthat is represented by general formula (I) in content of not greaterthan about 80 mol. %, and more preferably polymers that contain therepeating unit represented by general formula (I) in content of about 25to 55 mol. %.

[0060] It is preferable that the aminated phenol polymers mentioned initem (3) be aminated phenol polymers that contain the repeating unitrepresented by the general formula (III) in content of not greater thanabout 80 mol. %, and more preferably polymers those contain therepeating unit represented by the general formula (III) in content ofabout 25 to 55 mol. %.

[0061] The number average molecular weight of the aminated phenolpolymer (A) is preferably about 500 to one million and more preferablyabout 1,000 to 20,000.

[0062] The aminated phenol polymers (A) are generally prepared bypolycondensating a phenol compound or a naphthol compound withformaldehyde, to obtain a polymer that contains a repeating unitrepresented by general formula (I) or general formula (III), and thenintroducing a hydrophilic functional group (—CH₂NR¹R²) into theresulting polymer using formaldehyde and an amine (R¹R²NH).

[0063] The aminated phenol polymers (A) are used singly or bycombination of two or more.

[0064] Trivalent Chromium Compound (B)

[0065] For the trivalent chromium compounds (B), various known kinds canbe used, including, for example, chromium (III) nitrate, chromium (III)fluoride, chromium (III) sulfate, chromium (III) acetate, chromium (III)oxalate, chromium (III) diphosphite, chromium acetylacetonate, chromium(III) chloride, potassium chromium (III) sulfate, etc. Among those,chromium (III) nitrate, chromium (III) fluoride, etc., are preferable.

[0066] Phosphorus Compound (C)

[0067] For the phosphorus compounds, various known kinds can be used,including phosphoric acid, polyphosphoric acid and like condensedphosphoric acids and salts thereof, etc., where the examples of saltsinclude ammonium salts, and alkali metal salts such as sodium salts,potassium salts, etc.

[0068] Formation of the Resin Film Layer

[0069] Formation of a resin film layer on the surface of the aluminumfoil can be readily performed, for example, by applying an aqueoustreating agent that contains an aminated phenol polymer (A), a trivalentchromium compound (B), and a phosphorus compound (C) to the aluminumfoil surface, followed by drying through heating.

[0070] The aqueous treating agent is an aqueous solvent that contains anaminated phenol polymer (A), a trivalent chromium compound (B), and aphosphorus compound (C), and there is no limitation on theconcentrations of these ingredients. The content of each ingredient canbe suitably selected depending on the proportion thereof contained inthe resin film layer that is formed in the later step. The aqueoussolvent is generally water, but alcohols can be added thereto in orderto control the physical properties of the aqueous treating agent. As thealcohols, various known kinds can be used, including, for example,methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butyl alcohol andlike C₁ to C₄ alcohols. The amount of these alcohols relative to wateris generally about 20 wt. % or less and preferably about 0.5 to 10 wt.%.

[0071] It is preferable that the aqueous treating agent exhibit acidityof pH6 or lower. In order to adjust its pH, known pH adjustors can bereadily used. Examples of such pH adjustors include phosphoric acid,hydrofluoric acid, nitric acid, sulfuric acid and like inorganic acids,acetic acid, succinic acid, malic acid, citric acid and like organicacids or salts thereof. Examples of salts include ammonium salts, andalkali metal salts such as sodium salts, potassium salts, etc.

[0072] The resin film layer can be formed by applying theabove-mentioned aqueous treating agents to the surface of the aluminumfoil by immersion method, bar coat method, roll coating method, spincoating method, spraying method, and similar application methods, andthen drying by heating.

[0073] Drying by heating is conducted in order to vaporize the watercontent of the aqueous treating agent and to make the resulting resinfilm layer insoluble by accelerating the reaction among the aminatedphenol polymer (A), the trivalent chromium compound (B), and thephosphorus compound (C). Examples of energy sources for drying byheating include gas, electricity, infrared rays, etc.

[0074] It is preferable that the temperature for drying by heating be inthe range about 80 to 300° C. and more preferably in the range about 120to 250° C. The duration of drying by heating can be suitably selecteddepending on the temperature thereof, the amount of aqueous treatingagent applied, etc.

[0075] Inner Layer

[0076] The inner layer of the laminate for battery encasement of thepresent invention can be a single layer or a multi-layer of two or morelayers. It is preferable that among the inner layers, the layer exposedto the electrolysis solution be a heat adhesive resin layer.

[0077] Forming the electrolysis solution facing inner layer from a heatadhesive resin layer is advantageous due to the following reasons: Whena battery is manufactured using a laminate for the battery encasement,by thermally adhering the innermost layer to the metal electrodes thatcompose the battery, and by thermally adhering the innermost layers toeach other, it is possible to hold the metal electrodes in a sealedsystem that can reliably insulate the metal electrodes from outside air(particularly, water vapor). Furthermore, the adhesive strength does notsubstantially decrease even when the innermost layers are in contactwith the electrolysis solution for a long time. Moreover, even when thebattery is stored at a high temperature, occurrence of failures such asthe leakage of electrolysis solution, breakage, and the like can beprevented.

[0078] Taking the heat resistance and the like of the battery intoconsideration, for a resin to be used in the heat adhesive resin layer,it is preferable to use a thermal adhesive resin that has a meltingpoint of 80° C. or higher. In addition, from the viewpoint ofavailability and cost, olefin-based thermal adhesive resins arepreferable.

[0079] For such the olefin-based thermal adhesive resins, it is possibleto use a wide variety of known examples, including low-densitypolyethylene, medium-density polyethylene, high-density polyethylene,linear-low-density polyethylene, ethylene-u-olefin copolymer,ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer,ethylene-acrylic ester copolymer, ethylene-methacrylate copolymer,ethylene-vinyl acetate copolymer, ionomers, polypropylene, maleicanhydride modified polypropylene, ethylene-propylene copolymer, etc.

[0080] Among these, particularly preferable olefin-based thermaladhesive resins are polypropylene, maleic anhydride modifiedpolypropylene, etc.

[0081] The above-mentioned olefin-based thermal adhesive resins may beundrawn olefin-based thermal adhesive resins or uniaxially or biaxiallydrawn olefin-based thermal adhesive resins.

[0082] The inner layer may be composed of only by a heat adhesive resinlayer or by laminating a synthetic resin layer that comprises a singleor two or more multiple layers onto the heat adhesive resin layer.

[0083] Examples of resins, other than the above-described olefin-basedthermal adhesive resins, that may compose the synthetic resin layerinclude known polyester-based resins, polyamide-based resins,fluoroplastics, etc.

[0084] The synthetic resin layer can be obtained by forming the resinthat composes the synthetic resin layer into a sheet either withoutdrawing or by uniaxially or biaxially drawing, and then subjecting theresulting sheet to a known lamination method, such as dry laminationmethod, sand lamination method, etc., or subjecting it to extrusionusing a T-die extruder. When the resin that composes the inner layer isformed into a sheet, in order to provide the surface of the sheet withwettability, it is possible to apply corona discharge treatment and/oratmospheric pressure plasma treatment and like treatments for enhancingadhesiveness on the surface that needs such treatment.

[0085] Specific formation methods of the inner layer are as follows:

[0086] 1) The inner layer is formed by co-extruding maleic anhydridemodified polypropylene/polypropylene onto the surface of the aluminumfoil where the resin film layer is formed in such a manner that themodified polypropylene comes into contact with the resin film layer.

[0087] 2) A maleic anhydride modified polypropylene solution is appliedto the surface of the aluminum foil where the resin film layer isformed, and, after drying, an undrawn polypropylene film is obtainedthereon by thermal lamination.

[0088] 3) A maleic anhydride modified polypropylene resin is extrudedbetween the surface of the aluminum foil where the resin film layer isformed and the undrawn polypropylene film, and the resulting layers aresubjected to sand-lamination to obtain a laminate.

[0089] 4) A laminate is formed by adhering the surface of the aluminumfoil where the resin film layer is formed to the undrawn polypropylenefilm that has been subjected to corona discharge treatment using aadhesive for dry lamination.

[0090] The heat adhesive resin layer of the inner layer is used forfixing the electrodes of the battery by sealing them in without leavingspace between the layer and the electrodes. When the heat adhesive resinlayer is unduly thin, formation of pinholes tend to occur between theelectrodes and the heat adhesive resin layer during the thermal adheringprocess, and this may decrease the corrosion-resistance thereof againstthe electrolysis solution.

[0091] When the inner layer is made of a single layer, it is preferablethat the thickness of the heat adhesive resin layer that comes intocontact with the electrodes be about 10 to 100 μm and more preferablyabout 20 to 80 μm.

[0092] When the inner layer is made of two or more multiple layers, itis preferable that the total thickness of the inner layer be about 10 to100 μm and more preferably about 20 to 80 μm. In this case, it ispreferable that the thickness of the heat adhesive resin layer be about8 to 80 μm and more preferably about 15 to 50 μm.

[0093] A laminate having a structure in which the above-describedspecific resin film layer is disposed between the aluminum foil and theinner layer is satisfactorily usable as a material for encasing asecondary battery without being subject to an additional process.

[0094] Examples of the multilayer structures of the present inventionare as shown below.

[0095] Aluminum foil/resin film layer/maleic anhydride modifiedpolypropylene resin layer/polypropylene resin layer;

[0096] Aluminum foil/resin film layer/maleic anhydride modifiedpolypropylene resin layer/undrawn polypropylene film; and

[0097] Aluminum foil/resin film layer/adhesive layer/undrawnpolypropylene film.

[0098] Outer Layer

[0099] By providing an outer layer on the outer side of the aluminumfoil, it is possible to enhance the resistance thereof against externalforce, particularly against piercing, to the level comparable to that ofbattery encasement made from a metal can.

[0100] Similar to the inner layer, the outer layer may be a single layeror a multi-layer of two or more layers.

[0101] When the outer layer is made of a single layer, it is necessarythat the outer layer achieve the above objects itself. Therefore, it ispreferable that the resin that composes the outer layer have excellentmechanical strength and have dimensional stability at least to the levelthat can resist the heat during heat sealing. Taking these points intoconsideration, it is preferable that the resin that composes the outerlayer be a polyester film drawn in the biaxial direction, a polyamidefilm drawn in the biaxial direction, etc.

[0102] Examples of such biaxially oriented polyester films include, forexample, polyethylene terephthalate, polybutylene terephthalate,polyethylene naphthalate, polybutylene naphthalate, polycarbonate, etc.

[0103] Examples of such biaxially oriented polyamide films include nylon6, nylon 6, 6, etc.

[0104] When the laminate for battery encasement of the present inventionis subjected to drawing, a biaxially oriented polyamide film ispreferable because it has a greater elongation than that of a biaxiallyoriented polyester film.

[0105] From the viewpoint of protection effectiveness for the aluminumfoil, drawability, etc., when the outer layer is made from a singlelayer of a biaxially oriented polyester film or a biaxially orientedpolyamide film, it is preferable that the thickness thereof be about 6μm or more and more preferably from about 8 to 25 μm.

[0106] Furthermore, whether the outer layer is made from a single layeror multiple layers, it is preferable that the thickness of the outerlayer be about 30 μm or less in order to make the battery light inweight.

[0107] The lamination between the outer layer and the aluminum foil canbe conducted by known dry lamination methods, for example, a methodusing a dry lamination adhesive. In order to provide wettability to thesurface of the film, it is possible to apply corona discharge treatmentand/or atmospheric pressure plasma treatment and like treatments forenhancing adhesiveness to the biaxially oriented film that is used asthe outer layer on the surface that needs such treatment.

[0108] If necessary, it is also possible to provide a resin film layeron the outer layer surface side of the aluminum foil as on the innerlayer surface side.

[0109] The laminate of the present invention is suitably used as anarmored material for a secondary battery, particularly a lithium ionpolymer secondary battery.

[0110] Various known methods can be used to make the laminate of thepresent invention as a material for use as an armor for a secondarybattery.

[0111] Effect of the Invention

[0112] The laminate for battery encasement of the present inventionexhibits excellent gas impermeability that insulates the principal partof the main body of the secondary battery and the electrodes fromoutside gases (particularly water vapor gas).

[0113] The laminate for battery encasement of the present inventioncomprises innermost layer that exhibit excellent adhesiveness to metalelectrodes of a secondary battery. Furthermore, the laminate for batteryencasement of the present invention has excellent adhesiveness betweenthe innermost layers of the encasement.

[0114] The laminate for battery encasement of the present inventionmaintains excellent properties, such as stable thermal adhesiveness, gasimpermeability, etc., even when the battery is used under severeconditions.

[0115] The adhesive strength between layers of the laminate for batteryencasement of the present invention is not substantially deteriorated bythe gel electrolyte (gel electrolysis solution) used in the secondarybattery.

[0116] The laminate for battery encasement of the present invention iscorrosion-resistant against hydrofluoric acid generated bydeterioration, hydrolysis, and the like of the gel electrolyte that isused in the secondary battery.

[0117] The laminate for battery encasement of the present invention hasexcellent drawability, etc., and can be readily formed into apredetermined shape, leading to excellent productivity.

BEST MODE FOR CARRYING OUT THE INVENTION

[0118] The features of the present invention will be illustrated infurther detail below by referring to examples.

REFERENCE EXAMPLE

[0119] (Preparation of Aqueous Treating Agents)

[0120] The ingredients contained in the aqueous treating agent are asfollows:

[0121] Ingredients (A)

[0122] A-1: Aminated phenol polymer (a polymer having a number averagemolecular weight of 5,000 that contains 50 mol. % of repeating unitrepresented by general formula (I) in which X is a hydrogen atom, and 50mol. % of repeating unit represented by general formula (II) in which Xis a hydrogen atom, R¹ is a methyl group, and R² is a methyl group)

[0123] A-2: Aminated phenol polymer (a polymer having a number averagemolecular weight of 20,000 that contains 30 mol. % of repeating unitrepresented by general formula (I) in which X is a hydrogen atom, and 70mol. % of repeating unit represented by general formula (II) in which Xis a hydrogen atom, R¹ is a methyl group, and R² is a 3-hydroxypropylgroup)

[0124] Ingredients (B)

[0125] B-1: chromium (III) fluoride

[0126] B-2: chromium (III) nitrate

[0127] Ingredients (C)

[0128] C-1: phosphoric acid

[0129] C-2: polyphosphoric acid

[0130] Other ingredients (D)

[0131] D-1: zirconium fluoride

[0132] D-2: chromium (VI) oxide

[0133] D-3: polyacrylic acid (number average molecular weight of 10,000)

[0134] Per one liter of water, the above ingredients each having theamount (g) as shown in Table 1 were mixed,. preparing aqueous treatingagents (a) to (h). TABLE 1 Aqueous treating agent (a) (b) (c) (d) (e)(f) (g) (h) A-1 10 10 10 10 10 A-2 10 B-1 5 5 10 20 2.5 B-2 10 15 C-1 2020 20 40 20 20 30 C-2 20 D-1 5 5 D-2 2.7 D-3 16

Example 1

[0135] (1) Preparation of Aluminum Foil

[0136] An alkaline degreasing solution (2 g, product name: FC-315,manufactured by Nihon Parkerizing Co., Ltd.) was dissolved in 98 g ofwater to prepare an alkaline aqueous solution. The resulting alkalineaqueous solution was heated to 50° C., and soft aluminum foil (thickness40 μm, product name: BESPA 8021, manufactured by Sumikei Aluminum-FoilCo., Ltd.) was immersed in the solution for four minutes. Thereafter,the aluminum foil was washed with water and further washed withdeionized water, and then dried by hot air to obtain degreased softaluminum foil.

[0137] (2) Formation of Resin Film Layers on Surfaces of Aluminum Foil

[0138] On both sides of the soft aluminum foil that has been subjectedto degreasing treatment, aqueous treating agent (a) was applied using aroll coater in such a manner that the applied amount per each side was 2ml/m². The aluminum foil was then dried by heating at 180° C., formingresin film layers on both surfaces of the aluminum foil.

[0139] (3) Formation of an Outer Layer

[0140] To one of the resin film layers, urethane-based dry laminationadhesive (manufactured by Toyo-Morton, Ltd., product name: AD122/CAT10)was applied to the amount of 3 g/m² on a dry basis, forming an adhesivelayer. The adhesive layer was then adhered to a biaxially oriented nylonfilm (manufactured by Idemitsu Petrochemical Co., Ltd., product name:G-100) having a thickness of 25 μm on a surface that had been previouslysubjected to corona discharge treatment, thereby forming an outer layeron the resin film layer.

[0141] (4) Formation of an Inner Layer

[0142] To the other resin film layer, urethane-based dry laminationadhesive (manufactured by Toyo-Morton, Ltd., product name: AD-503/CAT10)was applied to the amount of 3 g/m² on a dry basis, forming an adhesivelayer. The adhesive layer was then adhered to an undrawn polypropylenefilm (manufactured by Futamura Chemical Industries Co., Ltd., productname: FCZX) having a thickness of 30 μm on a surface that had beenpreviously subjected to corona discharge treatment, forming a laminatefor battery encasement of the present invention.

Example 2

[0143] Preparation of the aluminum foil, and formation of a resin filmlayer on the surface of the aluminum foil and the outer layer wereconducted in the same manner as in Example 1. Formation of an innerlayer was then conducted in the following manner:

[0144] On the inner resin film layer, maleic anhydride modifiedpolypropylene was extruded using a T-die extruder in such a manner thatthe thickness thereof was 15 μm, and an undrawn polypropylene film(manufactured by Futamura Chemical Industries Co., Ltd., product name:FCZK) having a thickness of 30 μm was subjected to sand lamination,forming a laminate for battery encasement of the present invention.

Example 3

[0145] A laminate for battery encasement of the present invention wasformed in the same manner as in Example 2 except that resin film layerswere formed on both surfaces of the aluminum foil using aqueous treatingagent (b) instead of aqueous treating agent (a).

Example 4

[0146] A laminate for battery encasement of the present invention wasformed in the same manner as in Example 2 except that resin-film layerswere formed on both surfaces of the aluminum foil using aqueous treatingagent (c) instead of aqueous treating agent (a).

Example 5

[0147] A laminate for battery encasement of the present invention wasformed in the same manner as in Example 2 except that resin film layerswere formed on both surfaces of the aluminum foil using aqueous treatingagent (d) instead of aqueous treating agent (a).

Example 6

[0148] A laminate for battery encasement of the present invention wasformed in the same manner as in Example 2 except that resin film layerswere formed on both surfaces of the aluminum foil using aqueous treatingagent (e) instead of aqueous treating agent (a).

Comparative Example 1

[0149] A laminate for battery encasement was formed in the same manneras in Example 1 except that resin film layers were formed on bothsurfaces of the aluminum foil using aqueous treating agent (f) insteadof aqueous treating agent (a).

Comparative Example 2

[0150] A laminate for battery encasement was formed in the same manneras in Example 2 except that resin film layers were formed on bothsurfaces of the aluminum foil using aqueous treating agent (f) insteadof aqueous treating agent (a).

Comparative Example 3

[0151] A laminate for battery encasement was formed in the same manneras in Example 2 except that resin film layers were formed on bothsurfaces of the aluminum foil using aqueous treating agent (g) insteadof aqueous treating agent (a).

Comparative Example 4

[0152] A laminate for battery encasement was formed in the same manneras in Example 2 except that resin film layers were formed on bothsurfaces of the aluminum foil using aqueous treating agent (h) insteadof aqueous treating agent (a).

[0153] The proportions of ingredients in the resin film layers obtainedin Examples 1 to 6 and Comparative Examples 1 to 4 were evaluated in thefollowing manner:

[0154] The amount of carbon contained in 1 m² of resin film when theresin film layer was formed on the aluminum foil was measured using atotal organic carbon meter (manufactured by Shimadzu Corporation,TOC-5000A), and the value obtained by multiplying the measured carbonvalue by the coefficients shown below was defined as the content of (A).

[0155] The coefficient was defined as the value obtained by dividing theweight of polymer (A) by the weight of carbon contained in polymer (A),with the coefficients being determined by the type of polymer. Thecoefficient used for A-1 was 1.3 and that of A-2 was 1.4.

[0156] The contents of (B) (content of chromium) and (C) (content ofphosphorus) per 1 m²of resin film when the resin film layer was formedon the aluminum foil were measured using a fluorescent X-rayspectrometer (manufactured by Shimadzu Corporation, LAB CENTERXRF-1700).

[0157] As for (B), the contents of (D-1) and (D-2) per 1 m² of resinfilm were measured using a fluorescent X-ray spectrometer (manufacturedby Shimadzu Corporation, LAB CENTER XRF-1700). The content of (D-1) inthe resin film of Comparative Example 2 was 10 mg/m².

[0158] The content of (D-3) per 1 m² of resin film was measured byfollowing the same process for measuring the content of (A). Thecoefficient of D-3 used was 2.0. The content of (D-3) in the resin filmof Comparative Example 5 was 67 mg/m².

[0159] The measurement results. are shown in Table 2. The values shownin Table 2 are the contents of each ingredient in a single resin filmlayer formed on the aluminum foil. TABLE 2 Resin film layer Content ofContent of Content of aminated chromium phosphorus phenol compoundcompound polymer (calculated as cr) (calculated as P) Example 1 42 10 27Example 2 42 10 27 Example 3 42 10 27 Example 4 42 10 27 Example 5 42 1037 Example 6 84 20 54 Comp. Example 1 42 0 27 Comp. Example 2 42 0 27Comp. Example 3 0 11 27 Comp. Example 4 0 14 40

[0160] The laminates for battery encasement prepared in Examples 1 to 6and Comparative Examples 1 to 4 were immersed in an electrolysissolution (prepared by dissolving lithium phosphate hexafluoride inethylene carbonate to obtain a one molar lithium phosphate hexafluoridesolution) at a temperature of 85° C. The adhesive strengths of thealuminum foil against a maleic anhydride modified polypropylene film oran undrawn polypropylene film were then evaluated after 3 days, 5 days,7 days, 10 days, and 14 days from the start of immersion. Table 3 showsthe results.

[0161] As the criteria of the evaluation, a laminate in which thealuminum foil could not be separated from the maleic anhydride modifiedpolypropylene film or undrawn polypropylene film was evaluated as anexcellent laminate and expressed as A in the table, a laminate in whichthe aluminum foil could be separated but had not yet separated wasevaluated as a fair laminate and expressed as B, and a laminate in whichthe aluminum foil and the maleic anhydride modified polypropylene filmor undrawn polypropylene film were separated from each other wasevaluated as a defective laminate and expressed as C. TABLE 3 Evaluationof adhesive strength after after after after after 3 days 5 days 7 days10 days 14 days Example 1 B B B B B Example 2 A A A A A Example 3 A A AA A Example 4 A A A A A Example 5 A A A A A Example 6 A A A A A Comp.Example 1 B C C C C Comp. Example 2 B B C C C Comp. Example 3 B B B B CComp. Example 4 B C C C C

[0162] As is clear from Table 3, in the laminate for battery encasementof the present invention, separation of aluminum foil from the maleicanhydride modified polypropylene film or undrawn polypropylene film doesnot occur with the passage of the time. Therefore, the laminate forbattery encasement of the present invention shows excellentcorrosion-resistance against the electrolysis solution.

1. A laminate for battery encasement comprising aluminum foil and aninner layer, in which a resin film layer that comprises an aminatedphenol polymer (A), a trivalent chromium compound (B), and a phosphoruscompound (C) lies between the aluminum foil and the inner layer.
 2. Alaminate for battery encasement according to claim 1, wherein thecontents of the aminated phenol polymer (A), trivalent chromium compound(B), and phosphorus compound (C), per 1 m² of the resin film layer, areabout 1 to 200 mg, about 0.5 to 50 mg calculated as chromium, and about0.5 to 50 mg calculated as phosphorus, respectively.
 3. A laminate forbattery encasement according to claim 1, wherein the inner layer iscomposed of an olefin-based thermal adhesive resin and has a thicknessof 10 to 100 μm.
 4. A laminate for battery encasement according to claim1, wherein the inner layer comprises two or more layers, of which theinnermost layer is composed of an olefin-based thermal adhesive resinand has a thickness of about 10 to 100 μm.
 5. A laminate for batteryencasement according to claim 1, wherein the aluminum foil is softaluminum foil having a thickness of about 15 to 100 μm.
 6. A laminatefor battery encasement according to claim 1, wherein an outer layer isprovided on the aluminum foil on the side opposite to the surface wherethe resin film layer is formed.
 7. A laminate for battery encasementaccording to claim 6, wherein a resin film layer that contains anaminated phenol polymer (A), a trivalent chromium compound (B), and aphosphorus compound (C) lies between the outer layer and the aluminumfoil.
 8. A laminate for battery encasement according to claim 7, whereinthe contents of the aminated phenol polymer (A), trivalent chromiumcompound (B), and phosphorus compound (C), per 1 m² of resin film layerbetween the outer layer and the aluminum foil, are about 1 to 200 mg,about 0.5 to 50 mg calculated as chromium, and about 0.5 to 50 mgcalculated as phosphorus, respectively.
 9. A secondary battery using thelaminate for battery encasement of claim 1 as an encasement thereof. 10.A secondary battery according to claim 9, which is a lithium ion polymersecondary battery.